The ability to predict and generate responses with temporal precision underlies such crucial and diverse human capacities as associative learning, mastering complex movements, music as well as everyday activities such as driving, cooking;indeed, in the absence of a well-developed ability to ability to evaluate time, one would not be able to safely cross a busy intersection. The critical role in behavior played by temporal processing may also be illustrated by the fact that basic mechanisms involved in motor and interval timing appear to have developed early in evolution and been conserved. For example, a well-developed capacity for interval timing has been demonstrated in goldfish, starlings, rats, primates and humans. Indeed, as noted by Gibbon and colleagues, rats exhibit the same scalar property in interval timing demonstrated by humans but do not differ appreciably with respect to temporal precision. We propose a series of investigations to explore the neural basis of temporal processing in humans. Three types of studies will be performed. First, we propose to administer a series of investigations motivated by a contemporary model of temporal processing to subjects with brain lesions involving the basal ganglia as well as specific cortical regions (lateral frontal lobe, inferior parietal lobe;temporal lobe). By comparing the performance of subjects with different loci of brain damage and correlating performance with other measures of memory, language, attention and cognition, we expect to identify the brain regions and mechanisms underlying time processing. A second set of investigations will use functional MRI to explore the anatomic bases of temporal processing in young healthy subjects. Finally, we propose to use transcranial magnetic stimulation to identify specific brain regions that are necessary for normal temporal processing.